What I mean is you have to get the timing right...its last ditch but if you don't wait for the right moment, you still die.
And yes, if you are in the situation you mentioned, you have done many things wrong and probably deserve to die..but there are times when all your wingmen are dead and you are left with probably a couple bandits on your tail, the cobra could possibly help take out at least one guy with you before you go down.